The recently departed Channel 4 chairman Luke Johnson has hit out at the BBC's lobbying muscle, likening the corporation and its defenders to "Doctor Who and the Daleks joining forces to destroy the ultimate enemy".

Writing in today's MediaGuardian just a week after leaving the broadcaster, Johnson said he regretted the effort Channel 4 had expended trying to persuade the BBC to give up some of its licence fee money to other public service broadcasters.

"I failed to properly understand that the BBC is the single most influential lobbying organisation in Britain," he said.

"Whether it is backbench MPs on BBC local radio, print journalists on its payroll, ministers on the Today programme, tickets to the Proms or Wimbledon or Glastonbury, when its £3.5bn 'jacuzzi of cash' is threatened, the entire machine dedicates itself to seeing off any rival – rather like Doctor Who and the Daleks joining forces to destroy the ultimate enemy.

"The favours are gently called in, the army of public affairs staff get to work, and self-preservation on steroids kicks in."

Johnson also said the BBC had lost its nerve – unlike Channel 4 – and was now being "asphyxiated" by bureaucracy and political correctness.

There is no love lost between Johnson and the BBC director general, Mark Thompson, who defected from Channel 4 to go back to the corporation in 2004 soon after Johnson had started as chairman, despite giving assurances that he would stay put.

Pointedly, he branded the idea of Channel 4 merging with Channel Five – a plan first mooted by Thompson while he was Channel 4's chief executive – as "madness".

"If it gets revived then it should only be consummated if Five can be bought for £1," Johnson said. "Otherwise the deal provides poor value to the taxpayer and isn't a long-term solution to the structural issues facing terrestrial networks like C4."

In his review of his six years at Channel 4, he made no reference to Andy Duncan, whom he hired to replace Thompson as chief executive.